In this project we propose to use the considerable resources generated by the 4 cooperating networks in the "Family Blood Pressure Program" (FBPP) to conduct a genome-wide scan data for obesity. In the FBPP microsatellite markers were typed at a density of -10cM by the Mammalian Genotyping Service (MGS) in Marshfield, WI. The complete data set will include 9,940 individuals representing 4 ethnic groups (white, black, Hispanic and Asian). Obesity will be characterized as a weight/height ratio (body mass index) and waist/hip ratio. This data set will be larger than any prior genome scan for obesity, and the inclusion of multiple ethnic groups will make it possible to examine genetic heterogeneity. The specific aims of the grant are to conduct linkage and association analyses to localize regions influencing obesity. Investigators at the applicant institution will work closely with the FBPP Coordinating Center (Washington University, St. Louis) and investigators from each of the 4 FBPP networks. Evidence will be sought for consistency between results obtained from analyses of the genome scan performed by each of the individuals, and results summarized from the literature, with those found in meta-analysis. Despite intensive efforts the genetic basis of obesity has been difficult to establish. Linkage analysis using a genome-wide scan can potentially identify genomic regions not previously thought to be associated with susceptibility to obesity and provides a comprehensive test of the consistency of previous studies. The enormous data repository created by this project presents an important opportunity to make use of this technique.